Early Complications of Extracorporeal Shockwave Lithotripsy in The Records of The Department of Paediatrics, Nephrology and Allergology of The Military Institute of Medicine – Preliminary Results

Abstract The aim of the study was to analyse the frequency and type of early complications of extracorporeal shock wave lithotripsy (ESWL) and to assess the safety of the procedure among paediatric patients. The study is a retrospective analysis of all ESWL procedures carried out due to urolithiasis in 2009-2015 in the Department of Paediatrics, Nephrology and Allergology of the Military Institute of Medicine. Medical records of 170 children were analysed: 94 girls (55.3%) and 76 boys (44.7%) aged 1 to 18 years. Out of the 272 procedures performed, 247 were included in the study. Among 233 effective ESWL treatments, complications were noted in 35 (15.02%) procedures: among 10 girls (40%) and 15 boys (60%). In 25 cases (10.73%) surgical intervention was necessary due to urinary obstruction caused by a fragment of a disintegrated stone. Urinary tract infection was present among 3 patients (1.29%) who required surgical treatment. Nonsurgical complications included 7 urinary tract infections (3%) and 3 cases of severe abdominal pain (1.29%). Complications such as perirenal haematoma, subcapsular haematoma or ureteral perforation were not observed. The vast majority of complications observed in the study were associated with urinary obstruction caused by partial blockage of the ureter with kidney stone fragments (“steinstrasse”). Despite the complications that were documented, ESWL should be considered a safe procedure.


INTRODUCTION
Urolithiasis is a condition caused by the accumulation of deposits in the urinary tract which form when the concentration of soluble substances in urine exceeds the solubility threshold.
An increase in the incidence of urolithiasis was observed in recent years among both the adult and paediatric population, especially among newborns and infants. e prevalence of the disease ranges from 5% to 9% among adults in European registers [1]. Children represent approximately 2-3% of the total population of the a ected patients [2]. However, this number is most likely underestimated, as some studies suggest that up to 10% of the patients diagnosed with urolithiasis are children [3].
Children rarely present with classic symptoms of renal colic: sudden, acute, permanent or gripping pain located in the lumbar or hypogastric region, radiating to the groin, nausea and vomiting. Among the paediatric population symptoms are usually nonspeci c and dependent on the patient's age. e diagnosis of urolithiasis should be considered when a child presents with symptoms such as anxiety, abdominal pain, vomiting, fever, haematuria, recurrent urinary tract infections, spontaneous expulsion of kidney stones [4]. Usually urolithiasis does not lead to chronic kidney disease. However, bilateral or unilateral (in the case of a solitary kidney) urinary obstruction may lead to an irreversible loss of renal function.
Treatment of urolithiasis focuses on evacuation of the deposits and prevention of recurrence. Equally important is the protection of kidney function, prevention of urinary tract infections and correction of urinary tract anatomical aberrations. Furthermore, existing metabolic disorders must be diagnosed in order to ensure adequate treatment [3].
Conservative treatment of renal colic focuses on pain relief, appropriate uid therapy and treatment of urinary tract infections. Painkillers and antispasmodic drugs are used. Most kidney stones under 4 mm pass spontaneously [5].
Prophylaxis includes adequate uid supply, appropriate diet, regular physical activity and pharmacotherapy that accounts for detected metabolic disorders. If necessary, crystallization inhibitors should be administered [1,3].
Invasive procedures should be considered once conservative treatment is insu cient, usually when kidney stones exceed 5 mm in diameter. Minimally invasive procedures include extracorporeal shock wave lithotripsy (ESWL), ureteroscopic lithotripsy (URSL), percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS) [6]. ese methods have almost entirely replaced the classic surgical procedures. e patients' condition and diagnostic imaging should be taken into consideration upon deciding the method of treatment.
ESWL remains the method of choice for treating kidney stones measuring 6 to 20 mm and ureteral stones smaller than 10 mm. Exceptions include uric acid stones, for which pharmacological treatment is a method of choice. Absolute contraindications to ESWL include abdominal aortic aneurysm, renal artery aneurysm, pregnancy, ongoing urinary tract infection, haemorrhagic diathesis, anticoagulant therapy, bone deformities that prevent the patient from settling onto the exam table, urinary obstruction distant to the deposit (stenosis of the ureteropelvic junction, renal calyx, urethra and benign prostatic hyperplasia [7]).
ESWL uses high energy shock waves generated outside the patient's body to disintegrate the deposit into smaller fragments. e procedure is usually e ective if urine ow is unrestrained and deposits are located in the renal pelvis, upper and middle renal calyx, ureteropelvic junction and the upper part of the ureter [6]. Calculi located in the lower pole of the kidney are frequently di cult to excrete.
Complications of ESWL are a result of kidney stone displacement and fragmentation and of the direct impact of shock waves on the tissues. Early complications include skin lesions (reddening, bruising, petechia, necrosis), oedema of the renal parenchyma, haematomas, haematuria, proteinuria, dilation of the calyceal-pelvic complex due to urinary retention and hydronephrosis, "steinstrasse", urinary tract infection. ese complications are mostly temporary [6]. Actually, minimally invasive therapeutic options are used to treat most complications; it is mainly ureterorenoscopic lithotripsy (URSL) that is performed.
ESWL does not always lead to complete stone clearance. Residual fragments can be the cause of the recurrence of the disease. Late complications of ESWL such as renal hypoperfusion and renal hypertension have not been studied thoroughly, yet there is no evidence that they occur in the paediatric population. [8].
e aim of the study was to retrospectively analyse the frequency and type of early complications and to assess the safety of the ESWL among patients treated in the e study group consisted of 170 children: 94 girls (55.3%) and 76 boys (44.7%) aged 1 to 18 years (mean 10 years). Body weight ranged from 9.9 kg to 126.9 kg (mean 39.3 kg).
All the procedures were performed with the LITHOSKOP -Siemens multi-function lithotripter. e number of shock waves and their energy were individually adjusted to the age and weight of the patients treated. e range of energy used was 10-19 kV, the number of pulses 1500-3000 and wave frequency 70-90/min. All the treatments were performed under general anaesthesia. e post-procedural protocol included hydration, initially intravenous, followed by oral. Fluids were administered according to the patient's daily requirements, diuresis was not forced and no diuretics were used. In the rst days following the procedure, intravenous antispasmodic drugs (drotaverine) and oral alpha-blockers were administered to facilitate the expulsion of defragmented kidney stones. Antibacterial drugs were also used; their type was selected taking into consideration the clinical image. e procedure was considered e ective if the patient expelled fragmented kidney stones within 3 days a er the ESWL. As our focus was on early postprocedural complications, the stone-free rate was not determined (the success rate should be evaluated at least 3 months a er ESWL).

RESULTS
Out of the 247 ESWL treatments analysed, 14 were treated as ine ective, as the patients did not expel kidney stone fragments despite their disintegration. e e ectiveness in the study group was 94.3%. Only the 233 cases of e ective treatments were further analysed.
A total of 35 complications (15.02%) occurred among the e ective treatments, they a ected 10 girls (40%) and 15 boys (60%). Among 25 patients (10.73%) endoscopic surgical intervention (URSL) was necessary due to urinary tract obstruction caused by a fragment of a disintegrated stone. Two patients were additionally treated with double-J stent placement.
No signi cant early complications such as: perirenal hematoma, subcapsular haematoma or ureteral perforation were observed within the analysed group. As for mild haematuria, it was present in all the cases treated.

DISCUSSION
Extracorporeal shock wave lithotripsy is currently considered to be the method of choice in the treatment of appropriate uncomplicated cases of urolithiasis in children. It is considered to be safe and e ective, however, energy levels and the number of shock waves have to be watched carefully when treating children by ESWL to avoid severe complications. In the data available there is no evidence of long-term side e ects on kidney function in children, but the number of study samples is low and should be further studied. Early complications are described more o en; this was also the focus of the present paper [9,10].
Initially, young age was considered a contraindication to ESWL treatment, yet this view changed a er Newman's et al publication in 1980 [11]. Since then, an increase in the number of ESWL procedures among the paediatric population has been observed. e e ectiveness of ESWL treatment is usually determined by the total or almost complete (small fragments remaining) expulsion of the deposit and is assessed several months a er the procedure. e analysis by Nazli showed ESWL to be e ective in 67.9% to 92.85% of the cases [12]. e Polish population was studied by Bar, where the e ectiveness of ESWL ranged from 50 to 95% depending on the type of lithotriptor, and the size and location of the deposits [13]. Long-term follow-up and determining the e ectiveness of the ESWL procedure was not the aim of our study. It was, therefore, not assessed. e focus of the work presented was to analyse the early complications of the procedure. However, those complications (which result from the displacement of the calculi fragments) could only have been assessed among treatments where deposit disintegration was achieved. Hence, only the procedures e ective in that way were taken into account -94.3% (233 out of 247 treatments), which is comparable with the results achieved in other studies. It must be noted that ESWL is considered to be more e ective among the paediatric than the adult population. is may probably be explained by a more fragile calculi structure, a shorter, more exible, elastic Early complications of extracorporeal shockwave lithotripsy ureter and less di culty in passing disintegrated stone particles. Furthermore, less energy is required to disintegrate the calculi, due to children's thinner skin and smaller body volume [9,10].
Urolithiasis in the paediatric population was assumed to be more common among boys (the male to female ratio is 1.2:1) [3,12]. However, recent research reports no sex predominance, and even suggests higher disease incidence among teenage girls. Our records also showed female prevalence (1.23:1).
Early complications a er ESWL are rare; they occur in 3 to 7% of the cases and are usually mild and transient [14]. ese include mainly: skin lesions, haematoma, oedema of the kidney parenchyma and are an e ect of using shockwaves. Other complications include urinary obstruction caused by deposit fragments and require urological intervention. Clinical complications mainly manifest with haematuria, "steinstrasse" in the radiograph, renal colic or urinary tract infection [9,10,15].
In our research complications occurred in 15.02% (35) ESWL procedures, which is comparable to other studies. [14,15]. No skin lesions, haematomas, renal oedema were reported. However, 10.73% (25) procedures resulted in a signi cant dilatation of the urinary tract, which did not diminish with conservative treatment (antispasmodic drugs and alpha blockers) and required a URSL treatment (in two cases double-J stents were also placed) (Table I). Nevertheless, the bene ts and potential of ESWL procedure outweigh the signi cant number of surgical complications.
No serious early complications: ureteral perforation, acute pancreatitis, rupture of an aortic aneurysm, hepatic or splenic haematoma, gastrointestinal bleeding were observed in the study group. erefore, it can be assumed that the treatment was performed in a safe manner, which con rms the conclusions of other studies [10,16].
One limitation of this retrospective study is the short observation period. Moreover, we did not analyse the patient's age, size of the stones, their location and in uence on the number of complications, but we plan to extend our observations in the future.   CONCLUSION e vast majority of complications observed in the study were associated with urinary obstruction caused by a partial blockage of the ureter by disintegrated fragments of kidney stones. Despite the complications documented, ESWL remains a safe procedure on condition that it is possible to perform minimally invasive endoscopic procedure if necessary.